There is considerable prior art relating to the synthesis of 3-aminopropylmethylsilanes and siloxanes. U.S. Pat. No. 4,736,049 describes the hydrosilylation of allyl chloride by methyldichlorosilane to produce 3-chloropropylmethyldichlorosilane in 79% yield. In the prior art of producing aminoorganofunctionalsilanes as intermediates for silicones, allyl chloride is hydrosilylated with methyldichlorosilane. Significant amounts of by-products are formed in this reaction, including methyltrichlorosilane, propylmethyldichlorosilane and propene, necessitating distillation to purify the desired product. 3-Chloropropylmethyldichlorosilane may then be alkoxylated, typically with methanol or ethanol, to form the corresponding 3-chloropropylmethyldialkoxysilanes, in high yield, with formation of hydrochloric acid as the by-product. The 3-chloropropylmethyldialkoxysilane may then be converted to the corresponding 3-aminopropylmethyldialkoxysilane by ammonolysis, with requires high pressure equipment since ammonia is used both as a reactant and a solvent. Even with a large excess of ammonia, formation of the secondary amine, bis(dialkoxymethylsilylpropyl) amine occurs to a significant degree, diminishing the yield of the desired primary amine. Filtration of the by-product ammonium chloride is also required in this process.
British Patent No. 2,185,984 describes a synthesis of aminopropylsiloxanes, in approximately a 75% yield, by hydrosilylation of various ketimines, such as N-2(butylidene)allylamine, with bis(trimethylsiloxy)methylsilane, followed by hydrolysis. The resultant product is a mixture of 71-63% 3-aminopropyl- and 29-37% 2-aminopropyl-substituted siloxanes, indicating that this hydrosilylation process does not produce a single isomeric product. Separation of these isomers, by distillation, is difficult and the overall yield of the 3-(3-aminopropyl)heptamethyltrisiloxane is only slightly better than 50%.
European Patent No. 0 321 174 states that aminopropylsiloxanes can be prepared by hydrosilylation of allylamine with an organohydrogensiloxane in the presence of a base and a rhodium catalyst. Our attempts to duplicate this process failed.
A simple high yielding process for producing 3-aminopropylsiloxanes, substantially free of isomeric 2-aminopropylsiloxanes, has clearly been sought for years to no avail.